1. Field of the Invention
The present invention relates to a method for operating a connection in an ISDN network by integrating at least one intermediate system in which connections are led between subscribers of the ISDN network, whereby the protocols contain a terminal address, a caller identification and an identifier of the transmission service, among other things, the terminal address, caller identity and identifier of the transmitting service from the protocol being stored in a list in the intermediate system for each connection.
In the same way, the invention relates to an intermediate system which is integrated into an ISDN network, wherein connections are led between subscribers of the ISDN network via the intermediate system, and wherein a list is provided in the intermediate system for purposes of storing the terminal address, the caller identification and the identifier of the transmission service from the protocol for each connection.
2. Description of the Related Art
The ISDN communication system (Integrated Services Digital Network) is distinguished, among other ways, in that a number of auxiliary services can be made available by the network operator, the holding of connections being the service of interest here. In this auxiliary service, an existing connection can be shifted into hold mode by a subscriber and reactivated later.
The channel structure in ISDN comprises two useful channels called B channels, each with 64 kpbs, as well as one control channel, called D channel, with 16 kbps. The B channels serve for the transmission of useful information, namely data, voice or 3.1 kHz audio, whereas the D channel transmits control information. At a base terminal, called the So interface, up to eight terminal devices can be connected; a connection can exist via each B channel, that is, two connections simultaneously per base terminal. The ISDN system provides three protocol layers, layer 3 serving for purposes of connection control (connection setup and dismantling by means of call identification and identification of the transmission service, controlling of auxiliary services), layer 2 serving for terminal addressing, securing transmission, etc., and layer 1 serving for the physical transmission of all information in the B/D channels via the extension circuit.
The DECT (Digital Enhanced Cordless Telecommunications) standard was created for wireless communication over short distances and is used primarily for cordless telephones, or respectively, facilities. Basically, a radio connection is set up between a stationary part, which is connected to the stationary network, and one or more mobile parts, a useful channel with 32 kbps and a control channel with 2 kpbs usually being provided. DECT connections can also be utilized in a stationary manner between an interface of an ISDN network and the So interface at the subscriber side, particularly when a cable connection cannot be installed for structural reasons or would be more expensive than the radio connection.
It is thus desirable to produce, or respectively, to maintain an ISDN connection with an intermediately connected DECT connection, while limiting the performance features present in the ISDN system as little as possible. The invention is particularly concerned with the problem of making available the ISDN auxiliary service xe2x80x9chold (connections)xe2x80x9d when the connection is running via a DECT intermediate system (or several DECT intermediate systems). The ISDN protocol for xe2x80x9choldxe2x80x9d does not contain the parameters for identifying the transmission service in its data packets, this parameter being unnecessary, since the B channel structure in the ISDN system (64 kbps) supports all services.
The intermediate connecting of a DECT system would only enable this channel transparency if the DECT system was also based on a 64 kbps channel structure. But this is ruled out by the channel economy required in the DECT system.
It is thus an object of the invention to guarantee the auxiliary service xe2x80x9choldxe2x80x9d in an ISDN network even given the integrating of one or more intermediate systems, meaning primarily DECT intermediate systems, though it should also be possible to integrate other systems, be they wirebound or wireless.
This object is inventively achieved in a method of the type cited above in that, upon the arrival of the confirmation for holding a connection, the triplet (terminal address/call identification/identification of the transmission service) is marked; upon the arrival of a confirmation of the reactivation of a connection under the same terminal address, the marked call identification is searched for in the list, and a connection of the intermediate system which corresponds to the identification of the transmission service of the marked triplet is made available; and finally, the mark is erased.
The invention guarantees that in the restoring of a held connection, the intermediate system recovers the appertaining transmission service via a comparison of the stored and marked parameters.
It is expedient when the intermediate system is a DECT intermediate system and when connections between subscribers of the ISDN network are led via a first DECT station, an air radio link, and a second DECT station.
It is advantageous if, in the holding of a connection in the transmission service xe2x80x9cunlimited digital informationxe2x80x9d, the corresponding bandwidth is also held available for voice connections, and a modification onto half bandwidth is prevented.
It may also be expedient when a DECT channel that is already available is allocated to the connection that is to be reactivated, or respectively, when a new and appropriate DECT channel is selected for the connection that is to be switched back.
An intermediate system of the above described type is inventively characterized for purposes of achieving the inventive object in that the intermediate system and the list are designed to provide the triplet (terminal address/call identification/identification) of the transmission service with a mark upon the arrival of the confirmation for holding a connection, to search out the marked call identification in the list upon the arrival of a confirmation of a reactivation of a connection under the same terminal address, to make available a connection of the intermediate system which corresponds to the identification of the transmission service of the marked triplet, and to erase the mark.
It is advantageous here when the intermediate system is a DECT intermediate system, whereby the connections between subscribers of the ISDN network are led via a first DECT station, an air radio link, and a second DECT station, and a DECT station, and when a DECT station and the list are designed to provide the triplet (terminal address/call identification/identification) of the transmission service with a mark upon the arrival of the confirmation for holding a connection, to search out the marked call identification in the list upon the arrival of a confirmation of a reactivation of a connection under the same terminal address, to make available a DECT connection which corresponds to the identification of the transmission service of the marked triplet, and to erase the mark.